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🛡️ CVE-2024-47702 — kernel

🟠 CVSS 7.8 — High ✅ No Known Exploit NVD
7.8
CVSS Score
0 Low4 Medium7 High9 Critical10

Description

bpf: Fail verification for sign-extension of packet data/data_end/data_meta

In the Linux kernel, the following vulnerability has been resolved:

bpf: Fail verification for sign-extension of packet data/data_end/data_meta

syzbot reported a kernel crash due to

commit 1f1e864b6555 ("bpf: Handle sign-extenstin ctx member accesses").

The reason is due to sign-extension of 32-bit load for

packet data/data_end/data_meta uapi field.

The original code looks like:

r2 = *(s32 *)(r1 + 76) /* load __sk_buff->data */

r3 = *(u32 *)(r1 + 80) /* load __sk_buff->data_end */

r0 = r2

r0 += 8

if r3 > r0 goto +1

...

Note that __sk_buff->data load has 32-bit sign extension.

After verification and convert_ctx_accesses(), the final asm code looks like:

r2 = *(u64 *)(r1 +208)

r2 = (s32)r2

r3 = *(u64 *)(r1 +80)

r0 = r2

r0 += 8

if r3 > r0 goto pc+1

...

Note that 'r2 = (s32)r2' may make the kernel __sk_buff->data address invalid

which may cause runtime failure.

Currently, in C code, typically we have

void *data = (void *)(long)skb->data;

void *data_end = (void *)(long)skb->data_end;

...

and it will generate

r2 = *(u64 *)(r1 +208)

r3 = *(u64 *)(r1 +80)

r0 = r2

r0 += 8

if r3 > r0 goto pc+1

If we allow sign-extension,

void *data = (void *)(long)(int)skb->data;

void *data_end = (void *)(long)skb->data_end;

...

the generated code looks like

r2 = *(u64 *)(r1 +208)

r2 <<= 32

r2 s>>= 32

r3 = *(u64 *)(r1 +80)

r0 = r2

r0 += 8

if r3 > r0 goto pc+1

and this will cause verification failure since "r2 <<= 32" is not allowed

as "r2" is a packet pointer.

To fix this issue for case

r2 = *(s32 *)(r1 + 76) /* load __sk_buff->data */

this patch added additional checking in is_valid_access() callback

function for packet data/data_end/data_meta access. If those accesses

are with sign-extenstion, the verification will fail.

[1] https://lore.kernel.org/bpf/[email protected]/

How this vulnerability can be exploited

This issue can be reached with local access to the system, attack complexity is low, an attacker needs low-level privileges on the target. No user interaction is required. The scope is unchanged, so the impact stays within the vulnerable component. Rated impact: confidentiality high, integrity high, availability high.

CVSS metrics in full

The score comes from this vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

  • Attack vector: Local — a local account, shell or session on the host is needed.
  • Attack complexity: Low — the attack works reliably, with no preparation.
  • Privileges required: Low — an ordinary user account is enough.
  • User interaction: None — nobody has to be tricked into anything.
  • Scope: Unchanged — the damage stays inside the vulnerable component.
  • Confidentiality impact: High — total loss, or loss the attacker controls.
  • Integrity impact: High — total loss, or loss the attacker controls.
  • Availability impact: High — total loss, or loss the attacker controls.

Affected software

CVE-2024-47702 is recorded against 2 packages.

  • kernel (from 6.11.0 up to 6.11.2)
  • linux-kernel (from 6.11 up to 6.11.2)

Timeline and source

Published on 21 October 2024 and last revised on 12 August 2026. No public exploit is currently recorded for this entry. A vendor advisory or fix has been published. Record sourced from NVD.

References

git.kernel.org (Web)
git.kernel.org (Web)
git.kernel.org (Web)
github.com (Advisory)
nvd.nist.gov (Advisory)
git.kernel.org (Package)

Other advisories for this package

kernel has other advisories on record. If you are patching this one, these are worth checking on the same host:

CVE-2024-47702 on other distributions

Each distribution ships its own build and its own fixed version. Pick the one you run:

Details

Severity High
CVSS Score 7.8
CVSS Vector CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
CWE N/A
Public Exploit ✅ No
Source NVD
Published 2024-10-21
Updated 2026-08-20
Modified 2026-08-12

Affected Packages

Software From version Fixed in
kernel 6.11.0 6.11.2
linux-kernel 6.11 6.11.2

Similar Threats

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